High end to end values plus three cables in one circuit

[nc12345]

Hi guys

A little advice here would be much appreciated , it's been a long head ache day!
Had a ring circuit in a house today with high readings end to end on all three , they where in there 40s , 50s and 60s but got a good r1 + r2 and a good Zs , is this normal to be able to have high end to end values but the other other tests be ok ?

Also had another ring I presume but with three cables in . I was able to get end to end values between all three but these where also high and same again with good r1 + r2 and Zs . I'm thinking possibly a ring within a ring or is it possible to pick high readings up between different circuits.

It may be worth pointing out that most sockets had one cable in so I'm presuming plenty of joins and junction boxes under the floor but the floor has been tiled !

I hope this makes sense as I said it's been a long day ,

thank you to any replays in advance

 

[Richard Burns]

Not quite following your post in detail as I am not sure to what you are referring when you say good r1+r2.
Also not sure what 40s etc. means do you mean 0.40 ohms or 40 ohms.

However based on my interpretation of your post you have high end to end reading but OK zs readings (ignoring the r1+r2 bit), this is perfectly possible as there could be a loose connection somewhere but the single cable value may be complaint, although this still means the ring is not safe.

Since R1+R2 is calculated from the figure 8 readings (r1+r2/4) then if you have high end to end readings then it should not be possible to get good R1+R2 readings.

Single cables to all sockets on a ring sound like a spider ring from about 1950, I think. A single loop of cable with junction boxes to spur off to the sockets, not permitted now but should be able to test it OK, however the end to ends tend to be lower than expected.

Three cables in a breaker with end to end values across all possible combinations does sound like a double ring, possibly a spur socket added and then connected into the ring elsewhere; breaking down the circuit would find this one.

Did you ensure that your probes were in good contact with the cables? If so then it sounds like loose wiring in a specific socket (to affect all three conductors), you would need to go round the sockets to check the connections for security of fixing, not so easy for inaccessible junction boxes.

 

[nc12345]

Hi Richard

Thanks for the reply

The values where in the 40s not 0.40 and yes I got a half decent r1 + r2 which was what was giving me a headache !

I have checked all sockets for loose connections and as you said I fear a spider ring which I am unable to check the junction boxes due to tiled floors , obviously I wouldn't want to leave anything unsafe so not to sure what to do ?

I will purchase some new leads just out of caution as mine are a few years old also the customer showed me a test cert dated 2013 so I may well chase that up considering the amount of bodges!

also what would you suggest with the three cabled ring ?

thanks

 

[Richard Burns]

This is not an easy fix, you need to find out how the rings are wired, which is not easy with a spider ring. Make your best logical guess and go from there.

Initially do R2 (Rn,R1) tests from the consumer unit to each point and see where the reading jumps up, then the problem is either that point or the one before it in the ring or the JB under the floor for the spider ring.

For the three cable ring see if the ring is a spider then check any sockets for two cables, this may be a link to the "other" ring. If it is a standard ring then check for three cables. Split the circuit down, test continuity, and, if there is just a single double socket leave it as a spur, if it is a double ring with multiple sockets then you would need to remove the interconnection.

It may be possible to trace the circuit if you have a good tracer, but difficult under tiles under a floor without a CAT and genny.

If you are doing an inspection then just report it as a danger and maybe provide a quote for the repair if you can convince the client.
If you are doing an installation here then you should have checked first.

 

[telectrix]

is this a EICR? if so then give it a code 2 and advise customer that he may need new ceilings or tiles.

 

[nc12345]

Thanks for the feedback guys . This was not a EICR it was some few minor works with one notifiable which tested out great .
I didn't check the work too much as I poked my head under the stairs saw new bonding and a new board plus the client showed me the cert from 2013 which all checked out.
nevermnd I will head back with a fresh head and see what I can do .
thanks for the input

 

[Octopus]

If you are using a Metrel, maybe its time for new leads